Looks like you can mention anyone subscribed to Microsoft Teams(twitter.com)
twitter.com
Looks like you can mention anyone subscribed to Microsoft Teams
https://twitter.com/mr_timp/status/1156302426137214977
2 comments
Looks like various reports coming in stating that you're able to "@" mention people outside of your organization in Microsoft Teams.
Can confirm, although the list of people available in the mention seems to me limited. But it does display name and email address